Solved Exercises on Subtraction Within 5 in 1st Grade

Master subtraction within 5: basic concepts, counting backwards, and visual methods through these 3 detailed exercises.

Solution: Exercises 1 to 3
1 Basic subtraction
Exercise 1
Solve:
\(5 - 2 = ?\)
Definition:

Subtraction: Taking away objects from a group. Start with 5 objects, take away 2, count what remains.

Subtraction method:
  1. Start with the first number (5)
  2. Take away the second number (2)
  3. Count what remains
5
-
2
=
3
Start with 5
A
B
O
G
S
Take away 2
A
B
O
G
S
Remain 3
O
G
S
Step 1: Start with 5 objects

We have 5 apples: 🍎🍎🍎🍎🍎

Step 2: Take away 2 objects

We remove 2 apples: 🍎🍎~~🍎🍎🍎~~

Step 3: Count remaining objects

We have 3 apples left: 🍎🍎🍎

\(5 - 2 = 3\)
Final answer:

\(5 - 2 = 3\)

Applied rules:

• Subtraction: Taking away objects from a group

• Counting: Count what remains after taking away

• Visual method: Using objects to represent numbers

2 Counting backwards
Exercise 2
Solve:
\(4 - 1 = ?\)
Definition:

Counting backwards: Start from the first number and count backwards the amount of the second number.

4
3
0
1
2
3
4
↓
Step 1: Start at 4

We begin at the number 4

Step 2: Count backwards 1 step

From 4, we move back 1 step: 4 → 3

Step 3: The answer is 3

We land on the number 3

\(4 - 1 = 3\)
Final answer:

\(4 - 1 = 3\)

Applied rules:

• Counting backwards: Move left on the number line

• Subtraction: Each step backward represents taking away 1

• Number line: Visual representation of numbers in order

3 Subtraction facts
Exercise 3
Solve:
\(3 - 3 = ?\)
Definition:

Zero rule: Any number minus itself equals zero. When we take away all objects, nothing remains.

3
-
3
=
0
Start with 3
A
B
O
Take away 3
A
B
O
Remain 0
Step 1: Start with 3 objects

We have 3 bananas: 🍌🍌🍌

Step 2: Take away all 3 objects

We remove all 3 bananas: ~~🍌🍌🍌~~

Step 3: Nothing remains

We have 0 bananas left: 🚫

\(3 - 3 = 0\)
Final answer:

\(3 - 3 = 0\)

Applied rules:

• Zero rule: Any number minus itself equals 0

• Subtraction: Taking away all objects leaves none

• Identity: \(a - a = 0\) for any number \(a\)

Subtraction Facts Within 5
\(a - b = c\)
Basic Subtraction Formula
Subtract 0
\(a - 0 = a\)
Any number minus 0 stays the same
Subtract itself
\(a - a = 0\)
Any number minus itself equals 0
Count backwards
\(a - 1\)
Move one step back on number line
All Subtraction Facts within 5:
  • 5 - 0 = 5, 5 - 1 = 4, 5 - 2 = 3, 5 - 3 = 2, 5 - 4 = 1, 5 - 5 = 0
  • 4 - 0 = 4, 4 - 1 = 3, 4 - 2 = 2, 4 - 3 = 1, 4 - 4 = 0
  • 3 - 0 = 3, 3 - 1 = 2, 3 - 2 = 1, 3 - 3 = 0
  • 2 - 0 = 2, 2 - 1 = 1, 2 - 2 = 0
  • 1 - 0 = 1, 1 - 1 = 0
Key Subtraction Rules:

• Subtraction is not commutative: \(a - b ≠ b - a\)

• Subtraction makes numbers smaller: \(a - b < a\) when \(b > 0\)

• You cannot subtract a larger number from a smaller number: In 1st grade, we only subtract equal or smaller numbers

Visual Methods for Subtraction
\(5 - 2 = 3\)
Visual Subtraction
Visual methods:

Finger counting: Use fingers to represent numbers and fold down fingers to subtract.

Object manipulation: Use physical objects like blocks or counters.

Number lines: Move backwards on a number line to subtract.

Step-by-step approach:
  1. Identify the starting number: Show this many objects or fingers
  2. Identify how many to take away: This is the number being subtracted
  3. Remove the specified number: Cross out or physically take away objects
  4. Count remaining objects: This is your answer
Tip 1: Use fingers to solve subtraction problems up to 5.
Tip 2: Draw circles and cross out to visualize subtraction.
Tip 3: Practice counting backwards from any number.
Tip 4: Remember: bigger number comes first in subtraction.
Common errors: Subtracting the wrong way, forgetting to count what remains, counting the removed items instead of the remaining ones.
Practice strategies: Use manipulatives, draw pictures, count on fingers, relate to addition facts.
Important concepts to remember:

• Subtraction means taking away or finding the difference

• The answer to a subtraction problem is called the difference

• Always start with the bigger number first in 1st grade problems

• You can check your answer by adding the difference back to the subtracted number

Questions & Answers

Question: I don't understand how to do subtraction when the numbers are close together like 4 - 3. Can you explain how to think about it?

Answer: Great question! When numbers are close together like 4 - 3, here are helpful ways to think about it:

  • Count backwards: Start at 4 and count backwards 3 steps: 4, 3, 2, 1. You land on 1.
  • Use your fingers: Hold up 4 fingers, put down 3 fingers. How many are still up? 1 finger!
  • Think of it as "what's left": If you have 4 cookies and eat 3, how many are left? 1 cookie.

For 4 - 3 specifically, you're just taking away 3 out of 4 things, leaving 1 thing behind. It's like having 4 toys and giving 3 to a friend - you keep 1 toy.

The key is recognizing that when the second number is close to the first number, the answer will be small!

Question: Why can't I do 2 - 4? My older brother says it's impossible, but why?

Answer: You're asking an excellent question! In 1st grade math, we focus on subtraction where we take away fewer objects than we start with. Let me explain:

  • If you have 2 apples, you can't give away 4 apples because you don't have 4 apples to begin with!
  • It's like trying to eat 4 cookies when you only have 2 cookies - impossible!
  • In 1st grade, we learn subtraction where the first number is always equal to or bigger than the second number.

Later in school, you'll learn about negative numbers which allow us to do 2 - 4, but for now, we stick to problems where we don't take away more than we have.

So for now, always make sure the first number is bigger than or equal to the second number!

Question: How do I know if my subtraction answer is right? Sometimes I'm not sure about my answer.

Answer: Checking your subtraction is a smart habit! Here are ways to verify your answer:

  • Addition check: Take your answer and add back the number you subtracted. For 5 - 2 = 3, check: 3 + 2 = 5 ✓
  • Draw pictures: Draw 5 circles, cross out 2, count the remaining ones.
  • Use objects: Count out 5 blocks, take away 2, count what's left.
  • Count up: From your answer, count up by the subtracted number to see if you reach the original number.

For example, if you calculated 4 - 1 = 3, check by adding: 3 + 1 = 4 ✓ That confirms your answer is correct!

This checking method helps build confidence and catches mistakes early!